In another day of crazy, McDavid has really been shooting up the rankings in career playoff assists and points.
He entered this postseason with 46 assists and 75 points, which each ranked about 200th.
Entring tomorrow night's next do-or-die thriller, he now ranks 47th in assists, and 73rd in points. With the next 1-2 games of these playoffs, and even "just" a 30 point playoff run in 2025, he's likely to already be tied with Mikita in points with 150 at #30 and pass Thornton for the #25 with 103 assists. He'll still not even be 29 years old.
Whatever his body of work through 12 complete seasons is will likely see him widely known as the second greatest player to ever lace them up. From that point on, it's all gravy and possible accumulation that will make a not so small crowd wonder if he deserves higher.
As it stands right now his competition for second best ever (through 12 seasons) is Lemieux. I’m excluding Orr here as I never saw him, only played 12 seasons and was a defenseman.
Lemieux through 12 years had 3 Harts, 6 Ross, 4 Ted Lindsays, 2 cups and 2 smythes. 17 total big awards here. Lemieux’s adjusted totals through 12 (EVG/PPG/SHG adjustment) are 1253 in 745 GP for 1.68 ppg.
Considering that McDavid is already tied in Harts and Ted Lindsays with 3 and 4 respectively and that he is only behind in one Art Ross at 5, it is reasonable to assume that in the next three seasons he passes in all three. At least passes in two of the three with a match in the scoring title department. Regular season he should pass Mario.
He also is at 1038 adjusted points in 645 games as it stands now for 1.61 ppg. His last 5 years for adjusted ppg is at 1.77 according to this method. If continuing at that rate for three more years of an average of 79 games played we are looking at around 1458 adjusted points in 882 ish games for 1.65. Point being they would be almost identical statistically per game (era relative) with higher totals and he would have the more accomplished regular season resume. Your point about him potentially being ahead as number 2 is quite feasible.
For playoffs McDavid (adjusted) is at 117 in 72 games for 1.63. Lemieux, adjusted as well, through his first twelve seasons is at 134 in 89 games for 1.51. McDavid has the better playoff numbers for sure including the best individual runs when adjusted. The smythes and cups in Lemieux’s favor as of this moment would be helpful for him but we may be on the cusp of at least one smythe right now with three more years to go in this framing. No telling what can happen in three more potential postseasons. As of today it looks quite possible that McDavid can have the second best career (and through the 12 years you framed this in). I never thought I’d say that about a player if you asked me in 2014 but it looks to be a very good chance of being a reality just a decade later.