No, especially not now they've made the PC a customisable avatar for the player. Had they done this early on in the series, sure... But Pokemon just isn't a franchise where you play as the same character every time, unlike the Mario franchise or LoZ (sure, technically we get a different incarnation of Link every time, but still it's always Link).
That said, allowing us to give the protag a personality through choices we make would be pretty rad. Do you consistently pick the snarky replies? Well, NPC's might like you a whole lot less. Trying to avoid helping people out? They might see you as lazy. Always picking the 'brave' option and rushing headfirst into danger? People could consider you reckless.
I think there's definitely some room to play around with this
I don't think it's necessary or desirable for a main series protagonist to be voiced or have a pre-determined personality. More dialogue options and dialogue trees would be nice - you could have a system where the way you interact with your rival or the evil team leader would affect the way they view and address you, for example - but Pokemon isn't Mass Effect. We need to recall that the series is, ultimately, intended for children, and the blank protagonist is important for the purposes of immersion and wish-fulfillment for children. If GameFreak was to change anything about the way the protagonist is handled, I'd rather they implement a full character creator rather than voiced dialogue.
Now, in a spinoff game, sure, go wild. The Mystery Dungeon games already have pre-set dialogue and personality for the protagonist and it works fine for them.