Or Bethesda could have faith in their consumers.. Also Bethesda is rich.. They got money to last them a long time...
Amen to that. My personal interpretation, is that TES is a labour of love for Bethesda, in a way that Fallout isn't. I really hope that this translates into another mammoth expansion pack (a literal mammoth expansion pack would be amazing too - we help them gain independence against their giant overlords), before they pump out another round of Fallout to enable them to go crazy again on their next TES, Valenwood!
This post, of course, contains absolutely no speculation and is probably pure fact.