Are there any plans to give Easterlings and Haradrim their own factions? The same for the men of Dale?
The Edain Team has not officially announced anything regarding this matter yet.
What we know is that there is enough space for two more factions.
If Haradrim and Easterlings were ever to be made into an independent faction, it would thus be in a new faction on their own, yes.
The Men of Dale are currently implemented in the game as a
subfaction, belonging to Erebor, their main faction. I don't think there is any plan to create a further faction as it wouldn't be reasonable dividing them from Erebor, as Dale was not at all large and powerful enough to be equally compared to the other full-scale realms of Middle Earth during the War of the Ring.
Dale inevitably has a minor status and it's too much intertwined (dependent) with Erebor to do without it.
There is a
thread about a possible Evil Men faction that specifically gathers users' proposals in form of speculations in the Off-Topic section, given that it's been a custom so far (in the English forum, at least) considering them as not yet 'legitimate' Edain Suggestions and thus not worthy of being posted in the regular boards.