hi, i am from india & have worked on design and testing of analog vhf uhf transmitters.
the 500w tx in our design met spects for 30 km of range in uhf band, ( so called primery reception area ). secondary area ranged to 45 km ( noisy picture).
the switchover to digital is very very gradual, taking upto one or two decades, thereafter analog will be switched off.
one more thing there are transmitters now a days designed to work both in analog and digital modulation with little modification. there are some in india of same design working for analog as well as digital test transmission ( commercial broadcast is yet to begin).