I don't think it will take him that long to fill a top 4 role. Lindgren stepped into it almost immediately and Schneider is by all accounts a higher level talent
Maybe not, but we never know. Post draft, Lindgren spent 2 years in college and then a full year in the AHL. Even last year, he didn't make the team out of camp and started the year in Hartford. And it wasn't until he got paired with Fox that he really hit his stride.
Schneider is in his 1st post draft season, and he has played a very limited number of games, which could slow his progression. He is eligible for the AHL next year and could play the entire year there, barring a cup of coffee with the big club. He could then join the Rangers full time in his 3rd year, a full year sooner than Lindgren. And even if he might be able to handle more minutes as a rookie, there's no harm in him playing on the 3rd pair. That just means we can distribute the minutes more evenly. Maybe Fox doesn't have to play on the PK.
Of course, Lundkvist will be part of the equation too, assuming he isn't traded before then. Right now, neither Schneider nor Lundkvist are top 4 NHL players, so there's no point in stressing about it.