So you're kinda asking a multi-level question. So what will we do about Cally & Cap? What tradeable assets do we have? Our RHD options?

First is what our GM JBB said (I'm paraphrasing this quote) "Our priority is signing Point and we know we will have to shed 2 mid-level cap hits to do so." So think every forward in $4-$6M range. Next, look at who has NTC, modified NTC, and who doesn't have any (yet - July 1st) and that tells us who JBB is referring to.
Miller (has a lot of value, signed long term, great price, top 6 guy, power play guy, and a center)
Gourde (I don't see them moving Gourde cause they just signed him. JBB has said his style of play if how he is gonna build our team.)
Callahan (becomes an assistant coach, what? ... keep reading)

Now we could still try to move a NTC. Ask the player to waive it. Especially if we win the cup this yr. Think maybe an Alex Killorn. He has a NTC but holds a lot of value still. He is one of the reasons we have the number 1 PK in the league. Really clutch goal scorer in the playoffs. He gets 3rd line minutes here. Say we offer him a trade to his home town with the Habs. He would get PP time, top 2 line minutes, etc. His name (hopefully) is already on the cup. If he refused, we could buy him out as well as an option. Habs would jump at this b/c the ask would be very low. Why wouldn't you want him for next to nothing in return?

Callahan - I don't see them trading him with salary retained because we would likely loss assets in the deal. We can just buy him out instead of trading assets in that case. I can't see us keeping Cally, as must as he is loved and a leader, you can't pay a healthy scratch (or 4th line guy on this team) almost $6M. Faced with a buyout or trade to a non-playoff, rebuilding team willing to take on a contract for assets, (again hopefully his name is on the cup at this point,) I believe (just my guess) the Lightning offer him a coaching or front office job to retire early. This clears his cap but he still gets paid as a LTIR. He is a great leader in that room and would be a great assistant coach. Another option is offering another team assets to take Cally for the purpose of buying him out and then Tampa resigns him cheaper on a veteran deal. Of course, we could just straight up trade his whole contract and give up assets to do so for nothing in return but the cap relief. (Not a great option.)

Other roster assets, RFA rights to:
Erne
Paquette
Martel
I believe Paquette gets moved. We shouldn't resign them all with how much depth we have in Syracuse. He is a Center, he is having a career yr so he is now in his prime, and we have plenty of talent to replace him.

Other forward assets/ Syracuse:
ABB - Having a monster rookie yr and is too good to let go. He is probably off the board as a trade asset.
Verhaeghe & Stephens are 2 centers that could replace Paquette next yr. So they are NHL ready and one might be traded.
Biggest trade piece is Volkov. Scouted as the next Kucherov so why trade him? His is top 6 talent and there is no room in our top 6 in Tampa. He doesn't play that bottom 6 grit style, he is a pure goal scorer so we either waste his amazing talent in the AHL or trade him. He is very valuable as a trade piece, will immediately improve a team in scoring.
More names to watch. Katchouk, Conacher, & our goalie Ingram. Yep, I said it, Ingram might get traded. He is really good, AHL all-star, etc but he has no room in Tampa behind Vasy. Don't wanna sit a young talent as a number 2. Goalies need game time. Domingue is the perfect #2 so they may trade Ingram as an asset.

RHD -
In our system, we have Foote which has started to pick it up in Syracuse but scouts and people like Bolt Prospects on twitter (which is a great follow) says he is still at least 1/2 a yr away. So maybe a call-up Dec, Jan time next yr if he is proving to deserve it.
Also, Masin is in our system for the left side. Was one of the last cuts during training camp. He really impressed the coaching staff. Could cover LHD while Serg is on the right side. Masin is 23 years old and needs to take that next step and break into the league soon.
Rutta can be a cheap option for RHD.
The 3 UFAs Strals, Coburn, & Girardi. All are declining and would sign a "veteran" type low deal I believe. However, does Tampa want that with the league getting faster? I could see Tampa signing one of them, either Coburn or Strals if the deal is right and short term. I think Girardi retires.
Serg I think works all offseason to become better at the right side. He should be a top 4 D guy but can't be one on the left side behind Heddy and MacD.
Based on this without a trade or UFA not in our current system, next yr could be like this:
Heddy - Serg
MacD - Cernak
Coburn/Masin - Rutta (with Foote called up mid yr)

But I could see Tampa trading for an RHD at the draft. Remember some NTC kick in on July 1st. I could see a move like J.Faulk (Carolina) for JT Miller for example. Then our team is drastically better:
Heddy - Serg
MacD - Cernak
Coburn/Masin - Faulk
[Foote - 1 more full yr in AHL]

The crazy wild card for RHD still out there. Eric Karlsson. haha I know I know crazy. Tampa could move things around to fit him in (yes even with signing Point) but is it worth it? I don't know. Heard (even recently) podcasts/ lightning power play (a TBL radio station on iHeart) that they still believe Karlsson wants to come to Tampa. Even if he takes a huge discount/ short deal to go for the cup, I can't see him making less than Heddy on the discount. So again I don't know if it's worth it cause it really puts us in a bind the following yr for Vasy, Cernak, Cirelli, Joseph, and Serg. To me, Karlsson isn't worth the cap trouble.

So my guess is we do bring in one RHD this offseason like a Faulk, Tanev, Trouba (might be still too much $), Gudas, etc.

Thanks for reading this far. You asked a great question which has lots of layers so I wanted to give ya my guesses as a Tampa resident.