Right now the Pokemon series is at a point where there are only 8 or 9 unused type combinations left, to which point it seems like a sign for the upcoming next gen in the series to introduce new types, which we would be due for somewhere down the line so that types with only one weakness other then itself can have another weakness, plus changing things up with existing types is only doable in gens that introduce new types. But if Gen X does not end up being a time to introduce new Pokemon types, and seeing how many unused type combinations there are at the moment, I think that Gen X should introduce like only 3 first time type combinations with comes from the new Pokemon and new forms of existing Pokemon, same said with Gen XI on the same system. Of course the series should not ever get to a point where there's no unused type combinations left, not for 20-30 years anyway.