they won't invalidate heroic raiding - if they do actually have a 3rd season, the gear will probably at most be 710 ilvl, and then will just scale up to 740 or 750 to give the impression of gear progression
Isnt ilevel 735 mythic though?
If we went from 660 to 700, the next jump would be to 740. I guess they could just keep the pve ilevel 700 and then make the pvp ilevel like 750 or w/e. Kinda beats the entire point of the new gear system though, since originally they wanted numbers to not dramatically change vs players, but they are getting back there again.