Yeah from that perspective a move next season would make a lot of sense. This summer there might not be many high profile transfers in general, so possibly no knock-on effects either.
Next summer City might think about rejuvenating their squad a bit too, with Mahrez in his 30s. Foden might play more in midfield than he has etc. Plus Sancho would be cheaper then, which fits more into that price range they've been operating in. Not that it matters, but they wouldn't even have to make him their record signing. Like you said there's no indication of this happening, but a lot can happen in a year. Who knows how long Guardiola intends to stay though, especially if he wins the CL this year.
Chelsea, Liverpool and United will all have a better idea of what their squad needs by then, and likely have more money available too. I could see Chelsea replacing Ziyech for instance, and who knows what formation they'll play next season. United should probably give Amad a chance to see how he does having spent a fair amount on him, and see how Greenwood develops. Even Real Madrid or Barcelona might be an option, if they manage to offload Bale, Hazard, Coutinho or someone else.
Then again, if Sancho shines at the Euros some clubs might just get FOMO and try to make it happen this year. Or one big transfer leads to another, and so on