They will have to go narrowband just like all other VHF/UHF Public Safety frequencies.
The national interoperability channels (The names you have for them are wrong, btw) are already narrowband. They won't change.
Check your state's interoperability executive committee web site for any plans or documents. See the link at the bottom of this page Common Public Safety - The RadioReference Wiki
If agencies are using the VTAC, UTAC and or 8TAC channels in the P25 mode then they are not following the recommended national standard in the National Interoperability Field Operations Guide (NFIOG) that indicates all of these channels must be operated in the analog mode using CCTSS of 156.7 with a default of carrier squelch on the receive frequency, except for VTAC 33, 34, 35, 36, 37 and 38 which use a CCTSS of 136.5 with a default of carrier squelch on the receive frequency. No wonder radio communications between local, state and federal agencies are a cluster when a major incident happens. I sure wish everyone would get on the same page!
I was simply pointing out the national standard is listed in the NIFOG, not that the NIFOG is the official standard document. Much of the NIFOG contains the standard written by The NPSTC Interoperability Committee Channel Naming Working Group that was approved by both the APCO International Standards Development Committee (SDC) and the American National Standards Institute (ANSI). Every person employed in the public safety communications profession who has attended the Communications Unit Leader (COM-L) training course or the Communications Technician (COM-T) training course were given a copy of the pocket version of the NIFOG during their training and are urged to keep this document in their "go kit" for disaster responses. Many who have attended the COM-L and COM-T training courses may not necessarily be a member of APCO, so these individuals may not be aware the NPSTC Interoperability Committee Channel Naming Working Group wrote the standard or that the APCO International SDC approved them. I was only letting members of this forum who may not know there is a national standard for programming nationwide interoperability channels in public safety radios know that one does actually exist.