Reverse power creep!
Jk, likely rising voltage and electric terrain combos making it outspeed everything and ohko lots with specs
commented 10 minutes ago by ☆SleepyDreepy☆
Yes, this is probably one of your best bets.
Pincurchin being introduced would certainly help Alolan Raichu due to Rising Voltage and Surge Surfer, so you don't need to push it into a tier with Tapu Koko to use its ability properly, unless you'd like to set up Electric Terrain with the move itself as opposed to Electric Surge. A Terrain Extender also exists now, so Raichu has more turns to Rising Voltage + Surge Surfer sweep.
Also note that Heavy-Duty Boots have been introduced, allowing Alolan Raichu to pivot with Volt Switch without taking Stealth Rock / Spikes damage. Life Orb sets and even Choice Specs sets are popular, due to Surge Surfer making it extremely fast and both items boosting its power.
Alolan Raichu also gets Nasty Plot, yeah, I know that it got Nasty Plot in Gen 7, just pointing out that on Life Orb / Heavy-Duty Boots sets Nasty Plot is a great option.
Hope this helps! :)