Obsolete within a year, maybe - but still be in daily use
TETRA is used extensively and it won't be an easy upgrade if it can't be patched to cope seamlessly with both old and new standards. By way of example, in the UK, each regional Police force has its own budget. In order to swap their radio kit to a new standard, all forces would have to align their strategies and buying cycles. If not, they'd be pretty much obliged to stick to the old standard until their neighbouring forces had also upgraded. At a time when budgets are under huge pressure, I can't see this being a quick change for them.
Granted, some users (higher security users like government spooks and other very specialist sub-groups) might get new kit sooner - but the existing hardware is in the hands of so many 'normal' users it could take a while to effect a changeover unless in-field patching is possible.