First of all, there are a lot of upgrades that could be implemented to th10, as we've seen with barch and giants lvl7, archer towers lvl 13
who's to say that a lot of other buildings (like cannons, teslas) or units (like goblins, healers, dragons) might not get upgrades too?
If with each update we get 1-2 new upgrades, that would take a long time for th11 to be implemented. And I think it would be implemented ONLY if all the reasonable upgrades for th10 are released. By reasonable I mean not giving any more upgrades to already TH10 max level units (where you can only get them at TH10) like already, giants, barch, pekka, etc.
There's also tons of new content they can add, but I doubt they will deplete their ideas before upgrading to th11
In other words: not soon. not soon at all.
Also, I'm a mid-th8 and I hope to get to at least mid-TH10 before TH11

