As commenter the Samsung Secret tells it on XDA developers, there are a few kinds of updates for phones. Namely, critical, maintenance and feature updates.

正如三星批评家在《XDA开发者》所评价的，手机只有少量东西可以升级的，也就是，重要的升级，维护和功能升级。

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These steps are based on the original instructions at the xda-developers forum and require a copy of PTerm from the Android Marketplace.

这些步骤根基于在xda-developers论坛上的最初说明并且需要一份Android Marketplace上的PTerm软件。

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Update : If you need a hint, several commenters have pointed out posts on XDA Developers by ASUS' Gary Key indicating firmware 9.4.2.21 will arrive "by March 30th" so it shouldn't be a long wait.

ENGADGET: ASUS teases 'awesome new features' for Transformer Prime, doesn't say what they are (update)

G33k3r, Rohan32 and others at XDA-Developers may just save us from camping at the Google Play storefront through a new software hack.

ENGADGET: Rough hack converts an Optimus G to a Nexus 4, minus the constant sellouts

As it just so happens, a few lucky individuals have already done just that, and to prove it's momentarily possible, they've shared their success within the forums of xda-developers.

ENGADGET