You've got it wrong.
ID were bought by ZeniMax Studios which also owns Bethesda Game Studios (the development company) and Bethesda Softworks (the publishing company).
This is true, so I'd say ID has no authority regarding whether or not a new Elder Scrolls game will be developed, and if such a game is being developed or is to be developed, it will be Bethesda Game Studios, not ID that works on it. In short, I wouldn't worry about the Elder Scrolls series simply because ID is now owned by the same company that owns Bethesda.
This alone does not guarentee that we will see another Elder Scrolls game, of course, though I do believe we will, eventually, the only real guarentee we can have would be Bethesda actually announcing it, but it does mean that ID would not be the company to decide whether such a game is made or not.
ZeniMax is just power hungry for game companies these days.
I'd say they're just trying to compete with other big companies, like EA, I mean, just look at how many games have their logo on them.