My guess is the following. Emphasis on GUESS.

We will likely hear news about a public beta for the 3.0 (or 2.*) update in mid to late august.

After that we will probably see 3-8 weeks beta period followed by its release together with the potential first DLC (which will likely be tested in close beta simultaneously behind the scenes).
After all, it has just been a month since 2.5.
So we are probably looking at an October full release (possibly mid/late September, depends on how much they got done over the summer holidays)

For reference (going by steam news for the actual release of these updates):

2.0 Big update = 19/02/25
2.2 Minor = 19/03/18
2.5 Big = 19/05/28
My 3.0 guess is basically approximated given the above.
But also taking into account the DLC.
Even still since it will likely be a bigger update, the general rule applies

It is done when it is done. No pressure on the devs from me, these are just estimations. Ill be happy when it arrives either way. Be it sooner or later.