Nvidia will certainly try to get as much money out of ARM's R&D capabilities, existing IP, and future roadmap as they can. They will get their money's worth - at worst they will fail trying. In that sense, they won't destroy "ARM the company" or "ARM the IP". But Nvidia will have no interest in maintaining ARM's business model whereby ARM fosters a community of Nvidia competitors - they have an interest to the opposite. Therefore they very likely will destroy "ARM the ecosystem".