My priest has two professions - inscription and engineering. In case you didn't guess, inscription got a workout. I took Engineering to fill out my set of professions - plus Jeeves and a mailbox is usefull. To date; I have not made much gold from this toon.
Mists of Pandaria has something for the engineer in my priest - the opportunity to sell pets. Pet battles will be 'fun'. I have read (can not remember where) that pets will be casual friendly. You will be encouraged to look at your wins - and will be discouraged from looking at your losses.
My young child that sneaks onto my PC and take my ilvl 390+ tank Elwyn Forrest so he can duel lowbies - and lose; He also still watches pokemon. He will love pet battles - and is part of the target audience.
I have not bothered much with engineering pets before but have found few articles worth looking at:
- WoW Insider : guide to making BOE pets
- Kaliope's Engineering : Choose type of Miscellaneous, and 'check' small pet.
- MMO Champion Pet battle companion list
Like all speculative posts, if everyone jumps onto the bandwagon, then we may end up with oversupply and a price crash. For my personal opinion - I would be reluctant to call it an upcoming petmass just yet, but I do expect a huge demand for pets.