A microcontroller is just a lump of silicon - it doesn't appreciate your feelings of "loyalty", I'm afraid.

As Charles says, you need to judge this on the business case - not some notion of "loyalty".


Yes, of course there are costs to moving to a new architecture: obtaining new tools, installing/configuring them, learning them, etc...
Initially, your productivity will be lower, and the "quality" of your code is likely to be "lower".

You need to consider these things (and other) against the cost of the chips:

If you will only be making a few units, the cost of the chips will be almost entirely irrelevant - "lost in the noise";

If you will be making huge volumes, the cost saving on chips may well outweigh the "startup" costs.