Hey gamers, will our stats from Halo 3 and 4 transfer with us to the MCC? thanks in advance, spartans! 
No they will not.
From 10 years ago… from another system? Why?
Please tell me you aren’t serious.
Sadly… No. 
No. You start from scratch. Aren’t all of the different ranking systems from the Halo games removed anyway, and its all just under the 1-50 Halo 2 ranking system?
What would be the point in this? Yeah sure people worked hard at getting their rank ( not H4) but some people haven’t played the originals due to age or starting them too late and the games taken offline/ population drops. So no, everyone starts from scratch.