" Winninger did specify that the ruleset within the new books would be fully compatible with the currently existing Fifth Edition."
Its not a 6th edition, probably a revision like 3.5 was to 3e. 5E is extremely popular as of now, and there are still expansions coming out.
Even if it was a new edition, I doubt they'd change development, given that the game has been 4 years into it already, and progress has been very slow imo. Also, they don't want to fully implement the PnP rules.
