I expect even the teams on the "top" will get reeled in even closer to the rest of the pack. The Lakers have lost 6 of 8 on the road after their marshmellow starting schedule. Denver isn't anything special and has started to have issues with JR Smith. Dallas is playing above their heads right now IMO. They don't really scare anybody.
Only the last couple seasons. Part of the problem is the conference balance. All the teams in the west are rolling up wins on eastern conference teams, and beating the total shit out of each other. That circumstance leads to the tight standings we see now.
It's pretty extreme this season. It's another year where multiple teams that win more then 45 games will miss the playoffs while a couple of teams that win less then 38 games will make it in the East.
With all the teams at the bottom getting better, getting into the playoffs may take only 45 or 46 games this year. A lot of teams will be beating each other up the rest of the season. Every game is big for every team.