I'm putting my money on entry level kid friendly DMD machines. I'd say Jurassic Park, Last Action Hero, World Cup Soccer, Mario Bros, and Last Action Hero. I think any of the Data East DMD games are going to be worth 20% more this time next year than now.
I bought my first pin 3 months ago, a World Cup Soccer. I am in my 30s and wanted something to bite my teeth on my kids might like. People who grew up with 90s pins in the arcade are now getting into the point in their life where they can start affording this kind of luxury item, and I believe the bottom of the market is going to come up first. I personally am not really interested in anything without a DMD because it isn't nostalgic like the DMD machines are. This is going to raise the price of the B and C tier 90s DMD machines into the mid 3,000s. I personally was unable to secure a Jurassic Park the past few weeks, and none are available around me for less than $3,500. At that price, used newer Sterns start to make a whole lot more sense.
I sold my WCS94 a few weeks ago for more than I paid for it (but not more than I had in it) and had 3 suitors overnight when I listed it for cash. 2 of the 3 were first time pin buyers, about my age, with young kids. I am assuming that buyer will be looking for a place to put his second pin soon.
I believe the cheaper DMDs are going to be coming up in value next, as gateway pins to bring more hobbyists into the market.
Just my 2 cents.