Why I'm a Picoholic!
Yes, PICs are single source, but I know of no company that has a better record of making sure that there is stock out there. None of my clients has had any problems getting PICs for the projects I've designed for them.
Practical 8051's for use in a product as integrated microconrollers are not second sourced anyway are they? I mean we are way beyond using the stock original Intel clone parts! So, these are single source parts too. Not that this matters because of my fist point.
Consider that Microchip offers hundreds of different versions of these chips, and despite all that variety they all have common elements that make it easy to go to a new version.
I don't think Microchip has ever discontinued a part either. The only other company I can think of with this kind of record is Xilinx, and bravo to both of them. I have designed many parts into products that have become obsolete, it gives me peace of mind to know that Microchip is not apt to do that.
Also, consider that Microchip is actually making money in this business. It is far more likely that a company that is loosing money will abandon the business in the future.
One more bit of iceing on the cake, no single product line at present has more people familiar with it, so in the event a client of mine needs some help and I can't do it, what better part could I give them to allow another to do the work?
I think you can prob. find a PIC to do any task suited to an 8 bit microcontroller, from low power, to directly driving LCD displays, to USBs. The only thing they don't seem to have a line of super analog chip like the cygnal chips, except for the PIC1400, and that is not yet in flash technology.