Today, many microcontroller use in-system programming, or other system. So, why µVision could not include one in the next generation? I think it can be very usefull, no?
IMHO, it's not worth including in the toolset. Keil tools are software development tools, specialized programmers suit better for production. Besides, there is quite a variety of ways in wich in-system programming is implemented in different microcontrollers. Probably it's better left to 'third party' tools. There are other things to work on in the toolset, though. The optimizer could be smarter, and there is this annoying thing that *.c files with 'pragma asm' are recompiled at every build.