While none of Apple’s competitors will be thrilled with the arrival of iCloud, it is Research in Motion (RIM) who should be most concerned. This belief comes from Sterne Agee analyst Shaw Wu, who today issued his concern to investors, according to Apple Insider.

Apple’s iCloud service will be a “huge blow” to RIM, Google, Amazon, and Microsoft. However, Wu warns it will be BlackBerry creator RIM that will suffer the most, mainly because it offers its own unique push network.

Wu states:

“While iCloud doesn’t replicate all of RIMM’s push network, the ability for iCloud to offload data center processing and traffic from carriers is attractive. And it looks like AAPL will likely offer some base service for free.”

As a result, Wu expects RIM’s future revenues and gross margins to take a hit following Apple’s iCloud launch.

This is just the latest in a string of bad news for RIM to absorb.

Earlier this week, we reported the U.S. government is migrating to iPhones and away from BlackBerry devices. In March, RIM indicated its popular BlackBerry Messenger service would be coming to iOS in a move we said was the company’s “last reason to exist.”

Although Apple has confirmed iCloud, its details won’t come until Monday. That is when Steve Jobs is expected to give the keynote address to open the WWDC in San Francisco, California.

Despite the lack of specifics, iCloud is expected to include a music streaming component. In addition, Apple Insider believes other services, such as syncing of bookmarks, contacts, and calendar events, will be free for users who run Mac OS X Lion, Apple’s latest Mac operating system.

The iCloud service is expected to replace Apple’s current MobileMe product.

What do you think? Are RIM’s days numbered? Leave your comments below.