Not to mention this is the, what, 4th time Microsoft has attempted Windows on ARM? Every attempt they've done so far has failed miserably and there's no telling if this attempt won't also end in failure.
That's probably one of the reasons why JRiver wants to wait. To see if Windows on ARM finally takes off or dies a horrible death for the 4th time. There's no point in pursuing Media Center on Windows ARM if the platform dies AGAIN. Think about it, if JRiver invests both time and development costs on getting a Windows ARM binary going, only for Microsoft to kill support or adoption is nearly zero then it's nothing but a waste of money and time.
You might argue that since Apple has been successful with Apple Silicon thus far, that Microsoft will be able to do the same with their own ARM chips and Windows ARM support. But the situation with Windows is a bit different; Apple develops and controls all the hardware and the operating system of their devices and they're switching all Macs from Intel-based x86_64 CPUs to ARM CPUs, so it makes sense for them there. Apple did it right, they made sure the M1 Apple Silicon CPUs had pretty good performance and they made sure that the x86_64 emulation is nearly at native speeds (sometimes faster than native in some situations). Yet on the PC side of things x86_64 CPUs are going nowhere anytime soon, and they're certainly not in any danger of being replaced with ARM anytime soon. On the emulation front x86 emulation is a thing but there's a worse performance hit than with the M1 chips, with x86_64 emulation coming but still with a worse performance hit than the M1 chips.
I'd the chances that Windows on ARM will succeed this time around is still low but it's possible, Microsoft really needs to work on getting their x86/x86_64 emulation with a smaller performance hit. It's probably better to wait and see what happens in the next year or two with the platform before deciding to invest time and money into developing for it, in my opinion.
so likely ARM is the way to go, but indeed I would give it another year or so.
They've been saying this for years now yet Windows on ARM still hasn't taken off. There's no guarantee Microsoft will be able to duplicate what Apple has done with Apple Silicon with this newest attempt/push, honestly they'll probably end up dropping the ball again.
Like I said above just wait and see what happens with the platform this time around, I guess.
P.S. Personally I don't think ARM is the future. If I had to wager a bet, I'd be watching to see where RISC V goes, as I believe that's where the future is going to be.