While reading blue posts I got a conformation that you will NOT be able to level past 70 without the expansion.
Taar asks:
Will I be able to start leveling past 70 at midnight on Thursday, even if I do not have the expansion yet?
- Taar
Nethaera responds:
Unpossible.
https://blue.mmo-champion.com/1/12454631457-level-to-80-without-wotlk.html