On one hand, it would be foolish to turn off an income stream. OTOH, ongoing support for a past ed is what enabled the 4e/Pathfinder split in the community. WotC has committed to keeping 4e tools, but they will have to shut them down, eventually. Maybe with an 'upgrade' path, maybe by giving everyone with a 4e DDI 5e DDI, with 4e as a 'legacy' bonus. I'm not sure what would work best for them, and it may prove tricky, but if 4e continues getting support, even if it's just the odd dragon or dungeon, it'll form a core of resistance to 5e. It's not a matter of whether WotC will or should pull the trigger and quash 4e, it's only a question of when and how it'll be spun.