Nothing's going to happen in the next few months, not this year, but if the pandemic continues globally (and it certainly looks that way) and as more of the population gets vaccinated, then Thailand, and most other countries, will certainly make vaccination mandatory in order to get visas, and in my opinion, to renew visas for those foreigners already in the country. They may make exceptions to renew visas for any expats who cannot get vaccinated for medical reasons, but they are extremely unlikely to make exceptions for any unvaccinated Joe Blow tourist.
As for airlines not mandating vaccination for passengers, well Australia's Qantas has already stated several times that they are going to mandate it. And so will many other airlines. The most likely situation within another 1-2 years is unvaccinated people won't be able to do much at all other than stay home and watch TV. Proof of vaccination is going to be the only way to travel and attend concerts and get out into the world again.