Elder Scrolls has always been rpgs and never been multiplayer, so there is a convincing argument that they are turning against their roots to pursue a (more lucrative) target audience, at the expense of the single-player rpg enthusiasts the series has traditionally been aimed at for five games running now.
There's no evidence that this is going to be TES VI. If it turns out it is, count me as highly disappointed, but there is literally no evidence for that yet.
I think people who are disgusted with this move have every call to voice their opinion on this matter. If they are betraying what has been the genre of the series for so long now, we have to ask ourselves why, and historically speaking, there has been a recent trend with successful games switching genres to become MMOs or shooters because they are more profitable.
Betrayal is a very loaded term here. Is it so wrong to want to try new things? Personally I prefer that a company experiment and blend genres rather than put out the same old game over and over. To me, putting out a game that's been proven to sell well is more profit-oriented than taking a big risk in a genre you don't know if you're capable of handling. This isn't guaranteed to make them a lot of money, I'm actually more concerned about it
losing so much money that TES VI is hurt.
Therefore it is not unreasonable to think that this is a cash grab, or that it will put the series into stasis, or that it will destroy a gameplay style we have all come to love.
It is totally unreasonable considering we have heard barely anything on the subject. Any conclusions we come to are wild speculation but I really think you are overreacting with words like betray and destroy. Furthermore, I doubt it will put the series into stasis since they have been working on it since partway through Skyrim. It's obvious they have separate teams working on this and the mains series.