Some possible explanations: https://news.ycombinator.com/item?id=40506894

This stuff is decades old. It's completely legitimate that they may simply have lost the source code during a server migration or whatnot.

It may be common but let's not take the average companies lax attitude to source code archival and backup as "legitimate". It's a disgrace for the industry that this happens so often.

They didn’t announce it, the most likely explanation I’ve heard is that the original code is lost, along with Tiberian Sun

No, because Red Alert 2 Remaster exists...

Do you work for EA? Because they haven’t announced or released such a thing. A year ago a developer hinted there might be another remaster in the future, but it could just as easily be Generals as RA2.

No, that was gaming tabloids misunderstanding a sentence by EA a year ago. It was never announced.