ODI cricket is not saving us from some T20I takeover of the calendar, if you in fact have a look at things, our problem precisely right now is a clogged up calendar where we're trying to juggle 3 formats when we don't have to. If your argument is that T20 cricket is not cricket and might as well be a whole another sport, well ODIs aren't really cricket either, it's more like it but let's not forget it was a compromise. I wasn't alive when 60 over cricket was introduced but given how humans react to any change, I work under the assumption that it wasn't just embraced the moment it arrived on the scene, but what I am aware of without a doubt is the change in approach to batting it had on Test cricket, ODIs have changed the approach to Test cricket more than T20s could ever dream to.
T20 cricket is going nowhere and here to stay as the premier money format, Tests sure as hell isn't going anywhere either because duh it is cricket. I refuse to accept some bridge format at international level just because it has a bit of both when just embracing Tests and T20s would be easier, the 2 formats could work in harmony with the other, unlike the current paradigm where people keep telling us T20s are somehow threatening the existence of Tests, when in fact it's threatening the existence of ODIs.