Freedom, Freedom Unlimited, INK Cash and INK Unlimited are marketed as cashback cards, but they actually earn Ultimate Rewards points (which can, of course, be redeemed for cash.) It would seem straightforward for Chase to convert these to true cashback cards, and eliminate the ability to combine with Ultimate Rewards.

There has been speculation that Chase was considering this. I seem to recall it was originally based on questions from a Chase marketing survey. I expect there would surely be some advance notice.

Here is the previous thread: Chase survey regarding possible changes when combining points.

Note that Chase calls this process "combining", rather than "transferring", and I have edited the thread title to conform to their usage.