Perhaps. The LaLiga2 is already long enough as it is. By the time it finishes this year, LaLiga will almost be starting up again.
Well, this year is special. Whoever will be promoted from the playoffs won't have much time for rest, improve a team and prepare for the next season, that's true. It's also one of the reasons why I'd prefer Girona to be promoted. They have a core of the team who has already played in La Liga and they won't need to change much. Surely they would bring some reinforcements but they wouldn't need as much as Almeria (who would probably also lose Darwin Nunez and would need to replace him), Zaragoza or Elche.
But as a spectator I usually really like to watch Segunda playoffs in June when there is no other serious club football played. There are maybe NT games at that time but I don't like NT football too much. Even if it's Euro/WC I prefer to watch Segunda playoffs over most group stage games. I'm surely in minority though.