I don't know Marco, so I don't know his motivations or plans, but he's pretty disparaging of Android on his blog. A lot of what he says I agree with, but a lot of it reads like baseless commentary from the sidelines without having used the product much. So I wouldn't necessarily count on an Android client being his top priority.

If you can make your client work exceptionally well and fit the Android mentality, you have an opportunity to be fairly entrenched and beat out the official client - I wouldn't give up.

One thing Marco does well is think out every user interface decision and add polish to the product. If you don't do that, and he does release an Android client, that could kill your app's success pretty quickly. Polish is something Android is lacking pretty heavily, and we all notice it when it's there.