In addition to the subscriber issues already mentioned MARCS would have to purchase phase 2 software licenses for every repeater and comparator that would handle P2 traffic.
The license cost to upgrade a single repeater from P1 to a P1/P2 dual mode repeater is $ 16,000 (state contract cost). A system wide conversion to phase 2 will cost millions, converting the Cuyahoga County simulcast site alone would cost $ 3 million.
It's possible that some limited pockets of phase 2 operation could be seen in the future, especially if MARCS picks up more local government partnerships and builds new sites, but a system wide transition to P2 does not seem likely in the near future.
If MARCS is considering phase 2 the first indication would probably be some type of recommendation or mandate for subscribers to start purchasing phase 2 radios. APX radios don't do phase 2 unless the $ 320 phase 2 option is purchased with the radio.