Even assuming that 6E has a CC published SRD, there will be some folks that delay buying new stuff as they finish up current campaigns. Far easier to keep playing whatever version of 5E the group has years invested into then deal with piecemeal conversions as yet another 6E book trickles out. Also the cost of buying yet another edition will put some folks off even if they are D&D fans.And when that happens, what will the 5E holdout community look like? Will there be a Pathfinder like move by someone with the 5E ruleset? With 2 5E contenders in place -- ToV and A5E -- it seems like some portion of the base would continue playing 5E, but how many? How many current D&D players care about the specifics of the system?
But to tie back to the 'Best of Times' topic, there are already lots of 3rd party support for 5E and variants using a license that would be very difficult for Hasbro to cancel. Even if Hasbro commits a License PR oops V3, lots of RPG options for folks to pick from without any delay. There was a delay while Paizo spun up Pathfinder after the 3.5 -> 4 licensing mess.

