In addition to cutting 4,000 of about 20,000 workers, Motorola will close down or consolidate about one-third of its 90 facilities, the filing said.

The market seemed to like the job cuts and other moves. Google's stock price climbed 2.4% to $657.39 on the Nasdaq at mid-day Monday.

Nonetheless, some analysts said that Google's primary interest in Motorola could be for the patents, some of which date to the very creation of radio communications and therefore could form a broad basis for Google to defend itself in patent disputes from or others. Also, Google launched its own branded tablet in July, the Nexus 7, that is manufactured by Asustek, while Motorola makes its own tablets.

"If Google just wants the patents, which is of course possible, then it's just a matter of time before they let more workers go," Kagan said. But he also said that Motorola workers understand their product and if Google wants to continue such products, "it would make little sense to let the workers go."

Kagan added: "Either way, this is not the end. I see Google cutting more [Motorola jobs] as time goes by."