Question

If Venusaur receives the Chlorophyll speed boost, will it carry over when it Mega Evolves?

Answer 1

No actually

As Lupus said, Stat boosts remain. However, this means only the boosts like Swords Dance which actually take you to +2 will remain. Boosts like Chlorophyll which are caused by abilities and will only function as long as the Pokemon maintains that ability
So basically, Mega Venusaur will lose the speed boost.

However, do remember due to the mechanics of a Mega Evolution your previous speed is used to calculate who moves first on the turn you mega evolve. So the Chlorophyll boost will be taken into account on the turn Venusaur mega evolves but after that, dissappears.

Comments

yeah this is right

Answer 2

Unfortunatley no. The speed stat is raised while in the normal form but it isn't a stat raise or lower like speed boost, so when it gains its new ability it loses the speed boost.

Source: Here
Hope I helped!