If you want to look ahead, first look backwards. What's changed in the last 30 years? Minor stylistic changes in goaltending, plus new ideas in coaching and systems. Naturally, equipment is lighter and better. The league has increased by 10 teams. But the game is fundamentally the same now as it was then. Moving forward 30 years, I don't see any seismic shifts happening. A few more teams -- maybe 36? --, inevitable rule changes along the way, and improvements in monitoring technology. But hockey will remain the hockey we know.
Quick thoughts:
• I doubt the NHL ever expands overseas. Even if travel time improves exponentially, we're still stuck with 8-12 hour time zone differences, which would never work for players throughout a regular season, nor for audiences who wouldn't be able to watch live. And what about wildly different ticket prices and crowd sizes? Huge can of worms.
• However... I could see an annual series between the NHL champ and the champion of a European league. The Continental Cup? (Edit: Just checked -- that name is already used in curling). I could see a shortened NHL season balanced by an expanded international competition starting after the Stanley Cup is won in late May.
• Because of the increased international crossover, NHL coaches and GMs are hired from all across the globe. The quaint notion of only hiring hometown boys is over.
• Technology won't change players, but it probably will change the way the game is officiated. Chips in pucks, sensors within red and blue lines, and the goal line. Plus in equipment.
• Players themselves will have better health 'supplements' (legal, but manufactured), which will make for somewhat faster, stronger performances. Better medical/surgical treatments means longer careers -- more players in their 40s?