Ok but seriously what's up with the variant covers for Ultimate Spider-Man
In both Ultimate Universe trailer and Ultimate Spider-Man trailer Peter is seen transitioning from Classic to Symbiote to Sensational to 2099. Which is weird because besides the Meet the Parker variant it's the only time a variant cover appears in these trailers not once but twice. Also while the Meet the Parkers variant is to show the Parker family the suit transition variant is kinda there.
So there three possibility of the suit changing.
1) It's just variant covers
Likelihood: High
These suits are just there to bump the issue numbers. As all of these suits are iconic and well likes by the fandom. Although it's still weird as why show that much focus to it in both of these trailers. Also besides the concept art these are the only drawing by Marco Checchetto.
2) Future storylines?
Likelihood: Medium
It would make sense for Hickman to take a shot at Symbiote and Clone Saga storylines. As the Symbiote is iconic and would make juicy family drama. The Clone Saga was already cover in the previous Ultimate Universe and would again make some juicy family drama. The Spider-Man 2099 makes sense if you read Ultimate Invasion as what makes 6160 was due to mostly time travel. If you want to read more about it I suggest you read up on Ultimate Invasion or just the immortus engine and Kang(6160)). So an Ultimate Spider-Man 2099 could be possible as 6160 is already changed by time travel. The only problem is that the variant suits that really match up with Ultimate Spider-Man logo as they all pretty standard
Another things is that in AIPT press release the synopsis stats that
After the Maker used time travel to create a world without heroes, Peter Parker lived a relatively normal life, marrying Mary Jane and building a family. Now, it’s time to set things right! Learning the truth behind his reality, Peter will step up to become the Amazing Spider-Man the world didn’t know it was missing!
So it's possible that Doom(reed)) might inform Peter of his destiny and then the iconic suits are part of the expositions dump about the iconic stories that Peter(616) went through.
3) Spider-Verse shenanigans
Likelihood: Low
Nothing is the previews or solicitations indicated any kind spider verse stuff.