I'm betting on...
Either Clevo or Sager as the take-over target. Both of these companies have a great reputation in the "white box" marketplace with a range of excellently-spec'd system, innovative designs and small but healthy market shares. They would compliment/expand Acer's high-end footprint (Sager) and their convertible market (Clevo), and would effectively remove multiple house-brand competitors in one stroke. This would also allow Acer to tap into the low-margin/high-volume rebranding market...someplace that Acer has had experience in past lives.
Of course, I can't rule out something obtuse like buying Asus (and getting a whole lot of OTHER markets in addition to high-end laptops) or even Twinhead - my own personal machine label - a specialist in toughened portables for hard service and harsh environments. (Not an earth-shaking area to expand into, but one that's apparently attracting attention from the big names like HP and Dell).
Tough to call, but Clevo or Sager would give them a good mix to further beat up on Lenovo and add a good customer spread to their OEM house.
(BTW, I buy Acers for my family - like Mom and Dad. Great machines for the price, and run Linux well out of the box too!)