Will there be leveling guide addons for elder scrolls online?

Not likely, I think modern gaming has made these pretty obsolete.

Plus, that's what ESOHead is for.

If you want help leveling, try to stay at least 2-3 levels ahead of the content you are playing. Stay in The Wailing Prison/Coldharbour until you are level 3-4 and loot everything imaginable. Do not leave your starting islands until you are level 6-7. Collect every Skyshard you find and be sure to unlock combat skills immediately once you have a skill point. Be sure to add those skills to your hotbar immediately as well.

Get quest, do quest, complete quest, repeat.

Really it's pretty watered down already, I don't think you'll need one.