If they went PA-RISC and had software, the masses would have followed, I know I would have.
IBM Mainframe with MVS/zOS
PC with DOS/Windows
The masses voted with their wallets; software is too valuable to trash your system.
No new system (excluding game consoles and phones) has been successfully introduced in competition with the existing the past 25(30?) years. Even the Mac has kept compatibility in its many incarnations.
The trouble with introducing a new system is that you reset everything. Your old customers will not only be evaluating your new system, they will be comparing it to your competitors without giving you any inherent benefit. As happens in the game console market where they seem to be syncing releases with each other - customers have even less reason to be loyal or wait out in such a situation.