Any possibility of penals also getting 7th man?
Next to zero possibility. 7-man cons exist because the penal meta was massively dominating and cons were terrible, but then they had to nerf 7-man cons repeatedly because they were too good. Historically, an extra model for a squad in this game has caused many problems - 5 man grens (nerfed heavily and no one really uses them anymore) and 6 man fusiliers (complained about at least once a week).
As it stands, penals got some vet reworks to make them scale better into the late game (converted some offensive vet into reduced received accuracy - better this way as dead models can't shoot).