Pfizer is testing a few different next-generation coronavirus vaccines. The trial I'm in is testing the next-generation vaccine that is based on an enhanced spike protein. All the arms get BA.5 targeted boosters (what the current vaccine targets), so I'll have to wait to get the new XBB.1.5 targeted vaccines.
In animal trials these enhanced spike protein designs have improved the immune response from the original vaccine, so they are hoping these candidates serve as new and improved coronavirus vaccines. There's a 20% chance I'm just getting the current booster, and an 80% chance I'm getting one of the next-generation vaccines.
They've also got another next generation vaccine in trials that targets conserved areas of the virus. This one has a lot of promise as well. The idea here is to target areas of the virus that won't mutate as much. That's the holy grail of vaccines, but is easier said than done.