The way I look at sprint is that it's purely a benefit for melee since bard/machinist can dodge just as well without it, just with it on you have a bit more room for error but I don't think there are any AOEs or mechanics that you can't dodge without the use of sprint, so I think in the end it's going to help melee a little bit.
Historically everyone can dodge just fine without sprint. They'd have to actually start making mechanics that require sprint for it to be anything other than a bonus for all involved; melee have traditionally been able to dodge just fine, this is largely advantageous in that it'll make it easier to sneak in a greed GCD.
There are also a ton of 'things going pear shaped' situations where sprint will be advantageous for ranged--grabbing a button at the last minute, adjusting positioning because somebody else fucked up, flinging yourself face-first into a soak somebody else is about to miss, whatever. The current assumption is ranged will do it anyway, so not having to vent TP on a last minute push-the-button-so-mooncrops-doesn't-kill-us-because-the-healer-just-died will be a step up.
My assumption is that melee are going to get higher potencies and damage to compensate. I could be wrong though. I mean if their intent is for melee to ultimately deal more DPS than I don't see how else they could go about that. Could be that Bard and Machnist will get abilities that push the damage that melee jobs do above their own. We still don't know what the new Bard songs do for example, if they increase damage enemies take or if they take a penalty to their damage or anything like that.
And that's why them having stated an intention of any kind would be fantastic. We don't know what they intend to do at all, and this ending up a major nerf wouldn't be a good thing. ARR bard was capped as second-string damage, justified due to a hybrid of mobility and support stuff. In HW ranged eventually rose to parity as actual functional DPS, ending up a little overpowered. SB is spreading a lot of the traditional 'support' stuff amongst all DPS. RDM gets what amounts to a raging strikes that will also buff physical damage dealers in the party. Monk gets a party buff that will also feed them chakra.
We're at a point where being able to resource regen or buff party damage isn't a 'support' job thing anymore, so I'd rather they drop the support designation altogether and just let DPS be DPS and the utility each DPS provides be determined by what they cross-in for their individual groups. But, as you said, we know borderline nothing about the job skills or what the dev team envisions which is sort of the whole problem.
Ideally they balance shit out assuming 100% uptime keeps physical ranged competitive with other DPS; slapping a couple extra group buffs on us and then dropping us to 80% damage is a lot less appealing in a world where everyone brings something to the utility table.
The nearest point we could find out is when the NDA things goes up and the people who were invited to the media tour are able to post their findings.
It's super unlikely we'll get much out of the media tour that's nerd theorycraft friendly, due to a combination of what they'll focus on (which won't be potencies) and how in-flux some of the numbers may be. We should get vague ideas of what the jobs do, and it'll answer a bunch of broad questions, but I'd be surprised if we got a full list of potencies for all the skills/how ranged WD stacks up against other DPS in AF3 needed to really gauge things.