MIPS will not be completely dead, more like a zombie or the walking dead. It will still be used like PowerPC and SH are still used but no longer one of the mainstream high profile application processors like Intel and ARM. It may once again come back to life but it would require backing by a major player with deep pockets. China could have run with MIPS but they have a weak track record with software.
MIPS died because it lost the critical mass software support like Intel and ARM retain. If you don't have the software ecosystem and application developers your hardware is useless. Yes, MIPS did have software support but it was declining badly and getting left behind by ARM and Intel. Worse MIPS was eating majority of that software development cost themselves. Their biggest customer Broadcom was not helping them at all in this area.
Meanwhile ARM and Intel have built armies of software developers supporting their ecosystems and even better they are subsidized by their deep pocket customers. For example, ARM has Google and Linaro (i.e. TI, Samsung, IBM, Freescale), and Intel which doesn't even need subsidizing has enterprise server guys (e.g. IBM, RedHat, Novell, Oracle, Dell, ..). And that's not including all the open source guys and smaller companies working for free.
Also, MIPS didn't have a cheap development board which open source software hackers could support. All the Linaro guys have cheap development boards for Android and Linux hackers to work on. Cheap Intel boxes are everywhere. What did MIPS software guys have to work on that cost less than $300? Nothing!!! MIPS's customers like Broadcom don't offer cheap development boards only expensive closed proprietary reference designs. Yes, MicroChip has the PIC32 but that's a very low end MIPS core which requires their proprietary toolchain. Now compare that to a $35 Raspberry Pi (ARM-based) that is powerful enough to run Linux.
Moral of the story is its all about the software people.
I'm guessing ARM bought MIPS for their Simultaneous Multithreading (SMT or "Hyper-threading") know-how. ARM has steadfastly refused to implement SMT (and made some grossly inaccurate statements about SMT's power/perf) despite the fact that practically every other new CPU on the market (including Intel Medfield) has it.
When ARM eventually does implement SMT they'll probably refer to it by something like "Argon Mist" and claim that it's unique to the industry.
How is MIPS right move in the 3.5G-4G as reported by you going? Value of MIPS patents was value of MIPS patents when Sandeep Vij took over. Business sold for $60M - what a debacle. Blind trust in a mediocre executive by a reporter and being a free advertising vehicle is probably not considered good reporting.
ARM's interest squarely rests on the general patent protection. By being a part of the consortium which bought 498 patents out of MIPS' large patent portfolio (580 patents to be exact), they seek for the protection from any future law suits.
From what I understand, AST -- the consortium -- is not in the business of litigation, but rather, it exists to make sure these essential patents, such as those by MIPS, won't fall into the hands of patent trolls.
So Imagination seems to be replacing its own home-grown CPU for an industry standard one. Where does Imagination sell it's CPUs - do they expect to compete with ARM with their graphics-cpu combination - which markets?