I am sure they'll do 3-3-3. According to the WSJ article, majority of airlines have decided to do it that way, with only about 10% committed to 8-abreast.

Going from 8 to 9 give them 12.5% more seats to sell. That's a significant increase. CO may want to give it 32-33 pitch instead of 31. Going from 31 to 33 will cut seats by only about 6%. So, they'll still ahead.

Also, people usually pay more attention to seat pitch than width on paper. Airlines can more easily "sell" their increased legroom than increased width.