By now, you’ve probably heard the rumors that Google is set to unveil a full-fledged infrastructure-as-a-service offering at its annual Google I/O conference, which kicks off tomorrow.

If true, it’s a maneuver designed to take on Google’s cloud rivals at Amazon Web Services and especially Microsoft. But the real key here is going to be Google’s ability to recruit developers – and I’m not sure Google has what it takes.

The rumor was first brought into circulation by GigaOM’s Om Malik, who reports that his sources are indicating that Google is less jealous of Amazon’s mostly-startup customer base, and is more desirous of Microsoft’s obvious enterprise cachet and developer community.

Malik goes on to report that Rightscale and Opscode (developers of Chef) may well be signing on to provide their respective management and automation tools for this hypothetical cloud platform, which would boost overall appeal in general and help with the migration of existing cloud apps. And speaking of cloud app migration, today’s launch of CliQr, a Google Ventures-backed startup that boasts one-click redeployment to any cloud infrastructure, which could be a subtle on-ramp to a Google IaaS cloud.

Somebody please feel free to correct me if I’m wrong, but it seems that a new cloud.google.com landing page is indicating that Google is rebranding its cloud, including the Google App Engine PaaS, Google Cloud Storage and Google BigQuery big data analytics services, with the new name “Google Cloud Platform.”

This supposition is backed up by the existence of a Cloud Platform session track at the conference, which includes sessions focused on all of the above services, as well as the “Go” programming language that was founded by Google engineers. None of that is anything new – but it’s obvious Google would try to keep the really good stuff a secret. Oh, and Google is hiring engineers in a cloud platforms division.

Google App Engine has its share of developers, with Google claiming 150,000-plus building “mobile, games and modern web apps” with the PaaS right now. It’s unclear how many of those are actually enterprise-scale projects, and it’s a little disconcerting that they’re listing individual developers instead of vendors or organizations who’ve adopted it.

Here’s what I think needs to be announced tomorrow if Google really wants Google Cloud Platforms to be a hit, and unfortunately most of it means that Google finds itself in the rare position of having to play catch-up with Microsoft.

For starters, it needs to support some kind of open standard for virtual machine images, much like Windows Azure now supports the VHD format. Moreover, it needs to follow what developers want in their clouds, which would include the ability to deploy any PaaS they want (VMware Cloud Foundry and its forks, Red Hat OpenShift, or anything else) rather than forcing them into Google App Engine, as well as bolstering its framework and language support with things like Node.js. And it needs to add a really solid customer support offering.

In short, if Google’s serious about courting enterprise developers, it needs to really commit to openness, portability, and language support. But then again, that could be said about any cloud provider.  Hopefully, Google won’t disappoint.