This is something to think about.
It seems to me that there is a POWERFUL opportunity for Bethesda that has arisen from previous games that will reverberate thru all the future single player titles. In particular, ES5 should have an equal effect on ES6 as ESO should.
Lemme 'splain:
ES5 shows a Tamriel that is on the verge of profound change. The Imperial dominion has been shattered. Dragons have come back. An epic, existential conflict has begun between Altmer and Humans. Furthermore, there are tribes waiting in the wings to gauge the results and effects of these changes - the Sload, the Maormer, the Dunmer, the Argonians and all the Akaviri races.
Whatever happens in ES6 will be a big deal. It will set the stage for all the single player games that come afterwards.
This is also where the work put into ESO will have some weight. Granted - ESO has not been wholeheartedly adopted by the fan base. Will it survive on its own? I honestly have no idea. Is everything done in ESO copacetic with the single player series? Unlikely, though I would guess the differences aren't impossible to deal with.
What ESO offers, though, is huge - a platform (even if partial) to weave together all the provinces. Such a platform might require artwork, gameplay mechanic and feature modifications, but those could be done with some intelligence put into it (after all, there's undoubtedly a couple of things folks would like to see dropped from ESO, while wanting certain other things to be kept.)
From both a playing and business standpoint, there are stunning implications to this.
With some smart planning and imaginative developer teams, each single player game might become a 'module' that could be 'attached' to the next game in the series. The older games could be rewritten - not completely, but to the point that the provinces and a significant portion of their contents could, over time, be 'bolted in' to the 'common platform.'
The platform would have to be scalable. Also, if, say, ES7 or 8 required certain updates to lightly tweak combat, magic or whatever, those tweaks would have to be provided globally. It would constrain the devs from making any truly massive play style changes from game to game, but Bethesda shouldn't be too far off from an optimized interface and gameplay mechanic at this point - it's not like they don't have previous examples and work to base a 'final' I/F and mechanic on for all future titles.
I think it would be wise to begin pursuing this with the development of ES6, from a story, engineering and business POV. There are potentially huge advantages for all of us.
Thoughts?