“You won’t be disappointed,” wrote Steve Jobs a few weeks ago in one of his cryptic — and increasingly frequent — e-mail pronouncements.

This one was in response to a fan concerned that Apple’s (AAPL) Worldwide Developers Conference, which Jobs will kick off with a keynote address, had been upstaged by Google’s (GOOG) I/O conference a few weeks earlier.

But Google is likely to be the least of Jobs’ problems on Monday. For one thing, his speech comes less than a week after a widely re-broadcast interview at the Wall Street Journal‘s D8 conference that was one of the great Steve Jobs performances of all time. See here.

For another, the surprise value of what was presumably going to be his biggest announcement was spoiled when Gizmodo posted photos and specs of that lost iPhone prototype — the one with the front-facing camera. If Apple doesn’t unveil that iPhone on Monday and announce a June release date, the disappointment will be palpable.

But it’s likely that Apple has other tricks up its sleeve — some fairly predictable, some less so.

Below: our best guess for what they might be, in order of increasing surprise value.

• The latest iPad numbers. If Apple has sold significantly more than 2 million, we’ll hear about it.
• Price cuts on the year-old iPhone 3GS, likely to $99 from $199.
• A new browser to keep pace with Chrome and Opera. See here for the specs for Safari 5.
• A peek at Mac OS 10.7. This is a developer’s conference, after all.
• Refreshes for aging Mac hardware. The Mac Pro, Mac Mini and MacBook Air are all due for updates.
• A cloud-based version of iTunes to replace Lala.com. Apple didn’t buy the company last December and shut it down last week for nothing.
• Free MobileMe, so everybody can enjoy the benefits of wireless syncing.
• Some iPhone OS 4.0 surprises — beyond multitasking, social gaming, the new advertising platform. Our wish list includes Bonjour printing, iPad tethering and a video iChat client
• The revamped $99 Apple TV we’ve been reading about (and were told won’t be at WWDC).
• An iPod touch with a camera (the surprise would be if Apple didn’t save it for fall).
• A new iPhone carrier — if not Verizon (VZ), then maybe Sprint (S)?

Of course, the Apple faithful are likely to be disappointed no matter what happens Monday. They usually are. The build-up to these things is just too much. And lists like this don’t help.

In any event, we’re flying to San Francisco on Sunday and will be live-blogging the keynote — the gods of Wi-Fi permitting.

Tune in here Monday at 10 a.m. PDT (1 p.m. EDT) and keep your fingers crossed.

See also:

• Steve Jobs’ June 7 dilemma
• What Steve Jobs has up his sleeve

[Follow Philip Elmer-DeWitt on Twitter @philiped]