The most likely candidate for a late October/early November reveal is the rumored successor to the Microsoft Surface Book laptop. Microsoft unveiled the original Surface Book back in 2015, and a slightly updated model with the Performance Base in 2016.
I am not hearing that Microsoft is ready yet to take the wraps off the second iteration of its Surface Hub conferencing system or its Surface Studio all-in-one PC.
Perhaps the company could also announce a Surface Pro with built-in LTE support at Future Decoded, as well. Microsoft officials said earlier this year that the company would relent -- after claiming most users didn't want or need built-in cellular connectivity in their Surface devices -- and add LTE support to its Surface Pro line, but wouldn't say when they'd make such a system available or which type of processor it would run. Microsoft execs said earlier this year that they'd be supporting PC makers building both Intel- and ARM-based "Always Connected" PCs.
I tend to believe it's too early for Microsoft to show off the rumored "Andromeda" mobile device it's thought to be building. Andromeda is believed to be some kind of tablet/phablet, possibly with telephony capabilities. If and when Microsoft decides to take another stab at the mobile phone market, I'm thinking 2018 is a more likely target than this year.
For the past couple of years, Microsoft has held events announcing new Surface devices in New York City in October. I haven't heard if Microsoft still plans to do some kind of Surface announcement in New York this Fall, too, but I'm kind of doubtful, as what Microsoft is expected to show this Fall will be more evolutionary than revolutionary.