Right now the world is waiting on Nokia to make a stunning Windows Phone. The HTC Titan impresses, but it seems the Sea Ray will just be a smaller Titan. Nokia needs to make sure that their launch phone blows every other Windows Phone out of the water, not to mention the N8.
Screen size is a dicey issue, but 4 is the ideal size to launch at, it's the border where some people say it's almost too big, and others say it's almost too small, but most people say it's just right. It goes without saying that it will have a CBD Super AMOLED display. Follow up on the design of the X7 by having 4 front facing speakers, so you have true stereo in either orientation. Also, make sure that the screen is properly centred in landscape mode, and that the Windows Phone hard keys are opposite the Nokia logo and the speakers. The leaked Sea Ray photos and images suggest it will only be usable well in portrait mode, with landscape being a second class mode.
The camera has to be stellar, it should at the very least do what the N8 can do, but a slight bump to 13MP and a slight upgrade of the optics would be ideal. Nokia should forget about making the thinnest phone the Optimus Black didn't turn out too well for it, and the Moto Droid RAZR compromises the thinnes with the protruding camera module (as it should, but it makes the race to thinnest pointless, and Nokia shouldn't play a battle it can't win properly). Make sure that it's thick enough to hold comfortably in your hand, and thick enough that the camera button actually works like on another camera. A lot of phones these days with camera buttons get criticised for being uncomfortable to use. Nokia can deliver with being comfortable to use as a camera, and having the best sensor and optics available in a smartphone. Xenon flash goes without saying, even having a hybrid Xenon/LED set up so you can have extended LED lighting for videos, and keep the Xenon for pictures would be a nice extra touch.
For internals, there isn't much Nokia can do, but they should at least match what competing Windows Phones offer. The HTC Titan has a 1.5GHz Snapdragon with Adreno 205 GPU. The specs don't allow for anything higher at the moment, so Nokia should just settle with that (and later models they can easily go down to 1GHz or 800MHz like the HTC Radar). Since Windows Phone doesn't allow for removable memory, Nokia should also follow HTC's lead and go for faster eMMC flash, at least 16GB, but 32GB would be ideal even if there are 3 models of the same phone at launch with 8GB, 16GB and 32GB configurations at least one model beating out the HTC Titan is key. Fast integrated flash memory is key for good camera performance. Nokia needs to be able to push it as the best camera smartphone money can buy a 12MP+ sensor, excellent Carl Zeiss optics and Xenon flash are a good start, but the memory also needs to be so fast that the pictures are saved instantly so you can keep snapping photos without having to wait with the phone to catch up.
The one thing Nokia hasn't really messed with is their sound quality and reception, keep pushing it as the only real world phone with penta-band HSPA+, keep the excellent signal strength Nokia almost always brings to the table, and keep the natural sound reproduction that's characteristic of so many of their phones. Being able to toggle noise cancellation would be a nice touch, serving both people who like Nokia's way of doing things and those who prefer clarity over quality.
With a phone like this, Nokia can afford to charge $800 at launch (especially with the more full launch happening in 2012), the price is perfectly reasonable, and reviewers who get their hands on it will speak glowingly about how awesome the phone is, even if the price puts it out of reach for most consumers. With a phone like this, Nokia comes back with a splash.