What does Microsoft's special invite to Apple's iPad Pro event mean for the Surface Pro?

Microsoft was the surprise guest at today's Apple event in San Francisco with Kirk Koenigsbauer, Corporate Vice President for Office 365 Client Applications, extolling the virtues of Office and the Edge browser on the new iPad Pro tablet.

What made that surreal is that both companies have had a chequered relationship over the past 30 years, often regarded as being archrival with competing products.

Nearly 20 years ago, Microsoft bought $150 million worth of shares in Apple, a move that many said saved Steve Jobs' job (although that has been being hotly debated).

The deal was announced by Gates with the then-Microsoft CEO saying that it was "very exciting to renew our commitment to Apple".

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More importantly perhaps, Microsoft promised to deliver Office for Mac and Internet Explorer for Mac for five years.

Fast forward to 2015 and Apple has the upper hand and Microsoft is the one who has not been able to flawlessly execute its plans over the past decade.

The company is now worth more than $640 billion, making it nearly twice as large as Microsoft; the iPad, iPhone, MacBook family and the iMac are the industry benchmark when it comes to profitability and sheer volume sold.

With hundreds of millions of devices worldwide running in a tight, controlled operating system, Apple's installed base simply cannot be ignored; likewise, while Apple has the likes of Pages and Numbers to rival Microsoft's Office, they simply cannot compete, especially as Microsoft made these free for mobile devices.

So what's it all mean?

So, the appearance of Microsoft at Apple's event means that the frosty relationship between the two companies is starting to thaw. Microsoft is convincing itself that it is becoming more of a software/infrastructure vendor and leaving Apple to be the main driver for hardware.

Could Microsoft be looking to dilute the value of the Surface Pro 4, accepting that the iPad is the superior product when it comes to market penetration? It seems that Microsoft and Apple have decided to settle on their consumer positions for now with B2B being the next battleground.

Apple has already teamed up with Cisco and IBM to beef up its presence in the enterprise market and Microsoft announced yesterday that it has enrolled Dell and HP to become resellers for Surface Pro 3. Coincidence? Surely not.

• The iPad Pro: Everything you need to know about it.