That's the thing though - at his current pace Matthews won't need to continue racking up 50 goal seasons in his 30s. Here's a couple of ways it could play out if he plays till age 37 (which is young, he easily could play till ~40+ and score even more).
Age 27 - 65 goals
28 - 60
29 - 55
30 - 50
31 - 50
32 - 45
33 - 45
34 - 40
35 - 35
36 - 35
37 - 35
If he does this....that's 883 goals. That's with him not scoring above 40 goals once past age 33. Ovechkin did that 3x in a lower scoring league, for comparison.
More conservative, 5 less goals a year:
age 27 - 60 goals
55
50
45
45
40
40
35
30
30
30
Thats puts him at 828 career goals. And that's without him surpassing 40 goals a single time past age 31. Ovechkin surpassed 40 goals 5 times past age 31 in a lower scoring league (assuming scoring levels stay up) - so that's incredibly conservative.
As poster above point out - Brett Hull scores 509 goals past age 26 season, and that includes all of the dead puck era years. Matthews only needs 432 goals to reach 800.
Obviously - Matthews will need consistency, good health and to age well. If he has major injuries, or if he falls off a cliff in play, then it's not going to happen. But my point is - he just needs to age well - he doesn't need to age at an all-time great level (like Ovechkin did). He's in a great position to hit 800+.