My guess is we will get the option: standard say +2 str +2 con for your mountain Dwarven race OR you can take +2/+1 and place anywhere.
Oh hey, maybe a generalized version of this is an option. Either
1.) You get the default ASIs for your race (e.g., +2/+2 for Mtn Dwarf or +2/+1 for Hill Dwarf - in the specific ability scores) or 2.) You get strictly worse but free-floating ASIs (e.g., +2/+1 or Mtn Dwarf or +1/+1 for Hill Dwarf - in any ability scores)
People who don't want racial ASIs can still reach 16 in any two ability scores. But their character has spent so much effort overcoming their racial trait that they've suffered in properly developing other ability scores, as represented by the 1 less point.
