New Disney movies are released in DVD format similar to any other films of other studios. Dsisney also bring out new mastered versions or special editions of their classic movies on the special aniversary dates like 25th, 50th. But I have seen others that do not follow a clear pattern. For example:
Pinocchio USA home video release history
July 16, 1985 (VHS, Betamax and Laserdisc, Classics edition)
October 14, 1986 (VHS and Betamax, remastered Classics edition)
March 26, 1993 (VHS and Laserdisc, restored Classics edition)
April 16, 1995 (VHS, Spanish-dubbed Clásicos edition)
October 26, 1999 (60th Anniversary Edition, as well as a Limited Issue DVD)
March 7, 2000 (VHS and DVD, Gold Classic Edition)
March 10, 2009 (70th Anniversary Platinum Edition DVD and Blu-Ray)