The investment community has been on the edge since Apple (AAPL) dropped the bomb yesterday by saying its co-founder and chief executive was taking another medical leave, the third in the decade of his return to Apple’s helm. Since Jobs’ letter to Apple employees failed to mention any time frame for the leave, some investors hit the ejection handle as the shares lost six percent of their value in Frankfurt trading yesterday.

The US market was closed yesterday as the country observed Martin Luther King Day so Wall Street had ample time to digest the news. Early this morning AAPL fell 4.4 percent on Nasdaq where AAPL is currently trading at $333.18 a share, down from $348.48 last Friday, an all-time-high for the Californian consumer electronics powerhouse and the most-valued technology company in the world. Going for $333.18 a share, Apple’s current market cap equals to $304.69 billion.

But with Apple set to announce record-breaking December quarter today at 5pm PST (8pm EST), is the time right to buy AAPL now? Apple’s shares have been up 66 percent over the past twelve months. Any eagle-eyed investor certainly knew Wall Street would punish AAPL on the news of Jobs’ medical leave.

But conventional wisdom tells us that Apple probably sold an awful lot of iPhones, iPads and Macs during the holiday quarter. Mark Moskowitz of JP Morgan expects Apple to report sales of seven million iPads and 4.3 million Macs. Appleinsider quoted the analyst who wrote in a note to clients:

Our recent research indicates, however, that the actual iPhone numbers could track closer to 16.0 to 16.1 million units and iPad shipments could be 6.9 to 7.0 million units. We do not expect much of a delta to our current Mac unit estimate. We believe that the potential iPhone and iPad outperformance could add ‘at least’ $0.25 of EPS upside potential.

Analysts polled by Thomson Reuters expect an average earnings of $5.40 a share, a 47 percent increase. Quarterly revenue is expected to reach $24.43 billion, a 56 percent increase.

Philip Elmer-DeWitt at Fortune reported that bloggers are expecting per-share earnings of $6.32 on $26.4 billion in revenue, beating revenue estimates by a whooping $2 billion.

Andy Zaky, the founder and author of Bullish Cross - an online publication that provides in-depth analysis of Apple’s financial health – thinks the stock will sell-off after the market close later today. Zaky, who has no position in Apple, writes:

I think the stock is likely to sell-off a bit within a day or two after its report. It has tended to be almost always prudent to take profits whenever Apple has run-up big ahead of its earnings report and then gaps-up big in the following trading session.

The tendency has been to see Apple trade sideways to down from either its opening price after earnings or the following few trading session.

Traditional analysts agree, like Kathy Huberty of Morgan Stanley who advised clients that any drop in AAPL today"presents a buying opportunity ahead of earnings,she wrote:

We are buyers on any meaningful pullback of Apple’s share price. We expect the company to report strong December quarter results Tuesday night and continue to believe our bull case of CY11 $25 EPS (vs. consensus of $20.68) is increasingly likely on the back of stronger than expected iPhone/iPad shipments and gross margins.

She sees Apple reporting $23.9 billion in revenue and a per-share earnings of $5.25  based on an estimated sales of 16 million iPhones, 5.5 millions iPads, 17 million iPods and four million Macs. 

As for myself, I’m not going to advise you how to manage your investment portfolio, but some folks think today is the time to buy the shares as their lose some of the steam and sell them when AAPL goes back up following the earnings report. It’s the same buy-low-sell-high strategy that has served investors well thus far and it appears everyone’s expecting Apple to beat estimates after the bell anyway – and by a large margin.