Shares in Research In Motion declined from early morning gains on Tuesday to fall slightly after the company announced the release date for its new BlackBerry PlayBook tablet in both the U.S. and Canada.

The company's stock moved down 13 cents, or less than half a per cent, to $60.82 in midday trading on the Toronto Stock Exchange after gaining 44 cents earlier in the day.

RIM has pegged April 19 as the day that the PlayBook will appear on shelves in more than 20,000 retail outlets across North America. While Research In Motion (TSX:RIM) is expected to report strong quarterly results on Thursday, the PlayBook is seen as a key to its future success.

It's expected to appeal more to business users but the PlayBook will still have to compete against Apple's iPad and tablets that run on Google's Android operating system in the consumer market.

National Bank Financial Analyst Kris Thompson said he expects the PlayBook to sell just under 500,000 units by the end of May, with 350,000 of the tablets going to business users and the rest to consumers.

"In total, we expect RIM to ship 3.6 million units in fiscal 2012 and 6.2 million units in fiscal 2013," Thompson wrote in a research note, adding he expects RIM to grab about seven per cent of the tablet market in 2011.

RBC Capital Markets analyst Mike Abramsky said he expects the PlayBook to make a strong debut with RIM shipping 500,000 of the devices in its first quarter this spring.

"Given stiff competition from iPad 2 and Android, PlayBook will need to stake and hold its own ground in the rapidly expanding tablet market -- and we think PlayBook will have a strong debut," Abramsky said in a research note.

Abramsky estimated the PlayBook will add $3 billion in revenue for the Waterloo, Ont., company in its 2012 fiscal year.

The first generation of the PlayBook will rely on Wi-Fi short-range networks to connect to the Internet, initially without contracts with wireless carriers. It can be tethered to a BlackBerry to access email and is expected to provide the same level of security.

The units will range in price from $499 to $699 and be available at Best Buy and Future Shop stores in Canada beginning on April 19. However, the Waterloo-Ont.-based company says customers can place orders beginning today in stores or by ordering online.

The BlackBerry PlayBook will be available in three models, featuring 16, 32 and 64 gigabytes of storage capacity.

RIM also has said it will release other PlayBook tablets for advanced wireless networks, which will require contracts.