Mega Evolution would boost Hariyama's defenses.
So far Game Freak confirmed that Diancie, Metagross, Sableye, Sceptile and Swampert will receive a Mega Evolution in the upcoming Pokemon Omega Ruby and Pokemon Alpha Sapphire titles.
I'm hoping that Game Freak will announce a Mega Evolution for Hariyama, a Fighting type Pokemon, which retains its hidden Sheer Force ability (boosts the base power of all attacking moves that have an additional effect by 30%, while nullifying all additional effects).
Mega Hariyama would receive a boost in its Attack, Defense and Special Defense stats, while lowering its Speed stat, as seen in the chart below:
| Stat | Hariyama Base Stats | Mega Hariyama Base Stats | Change |
| HP | 144 | 144 | - |
| Attack | 120 | 140 | +20 |
| Defense | 60 | 90 | +30 |
| Special Attack | 40 | 40 | - |
| Special Defense | 60 | 130 | +70 |
| Speed | 50 | 30 | -20 |
| TOTAL | 474 | 574 | +100 |
Those stats along with EV boosts could allow Hariyama to survive an additional turn. Imagine striking a bonus Close Combat on your opponents!