I would say that 6e would be viable only if they have a better system. I started on the brown books, quit after seeing 2e, kept tabs upon but did not play 3e, 3.5e, and 4e, but returned on 5e because they finally fixed a lot of what I hated. If they want me to buy 6e, they would have to have a significant improvement on 5e. Not just different, but better. A more dynamic damage range, a better skill system, armor rules that have a more significant impact, that sort of thing.
But if its just going to me tweaked races, classes, spell lists, and feat options, they're wasting their money.
What I would like to see is a basic system ala the PHB, and then modular rules for combat, skills, etc, that a GM can add if desired but still fit with the PHB. That way a group, such as mine, that does a lot of investigative scenarios could benefit from a more detailed skill system that can be fine-tuned, and so forth.