I don't
think it will be All Stars but at the same time I wouldn't be too surprised honestly. The more years you wait the harder it is to get the people you want to cast since people will be more likely to have moved on. Making them more frequent makes All Stars seasons more manageable but probably not as "star-studded".
Although I like to see the new casts anyway so I don't mind if they never have an All Stars season. Having a few returnees is fine by me but I prefer a new cast more than that too.
Entertaining the idea..... It'd be easy to make it a "Second Chances" season, or even an All Stars season with that kind of theme around it, as they could justify almost anyone getting picked from the first 3 seasons. The only houseguests that wouldn't be eligible are Jillian, Jon & Sarah. 2nd & 3rd place finishers would make perfect sense to include in that type of season. They also had a lot of memorable players who got evicted on double/triple evictions and got screwed by a twist or in some other fashion who would make sense.