What Nvidia has in mind.
Nvidia's plans for ARM are clear if you think about what they are saying. The key phrase is here:
"We will maintain its open-licensing model and customer neutrality, serving customers in any industry, across the world, and further expand Arm's IP licensing portfolio with Nvidia's world-leading GPU and AI technology," he added.
They quite clearly intend to tie in licences for ARM CPU cores with licenses for Nvidia GPU cores. That is, in order to buy an ARM license you will also need to pay for an Nvidia GPU license, whether you use it or not. The ARM CPU licences can remain reasonable, but the associated GPU license will become increasingly eye-wateringly expensive and with ever increasing restrictions on what you can do with it in order to segment the market and extract the maximum possible revenue from each customer.
Want to build a phone with an ARM CPU? You will have to pay for an Nvidia GPU even if you use a different one. Want to build a server with GPU acceleration for AI? Your only GPU choice will be Nvidia, and you will have to sign a "partnership agreement" with Nvidia to license whatever AI software framework they are promoting that year. Want to build a CPU oriented towards cheap Raspberry Pi like devices? Sorry, but your product doesn't fit in with their market strategy and their salesmen have got other more lucrative things to do than to talk to you about it.
Having ARM owned by Nvidia will also bring it under US export controls, and the US have already tried to stop ARM licensing to Chinese firms. Trump may be gone, but that policy will survive into the future as there are simply too many interests in Washington who want to carry on a trade war with China by all possible means. Over the long term being used as cannon fodder in a war will sink ARM, as nobody outside of the US will be able to trust them any more and companies will drift towards other solutions which are not subject to the same risks. Britain will then lose the flagship of its high tech industry, as just another casualty in a foreign war.
I think that ARM needs to remain under UK control, and the UK should be identifying other companies in a similar position and acting to protect its national IP from situations such as this. Foreign investment should be welcomed, but commercial monopolisation (of the GPU market in this case) or foreign political control (US export laws) should be prohibited.