Maybe these companies will have a strong voice in the decision, and maybe even small shareholders will realize that Bitcoin can bring them profit. Should the decision be positive, it would definitely affect the price of BTC, because people would take it as a really big deal.
Big share holders in Microsoft Board Members have biggest powerful voices in any vote, and if they don't want to invest in Bitcoin, they will vote against (veto) this idea. Small share holders can raise their voices through votes that mean nothing to decide the company decision to invest in Bitcoin.
If Microsoft or any Big Tech invests money in Bitcoin, it will be great news for Bitcoin community as it shows Bitcoin adoption again shifts upward more considerably. Nevertheless, they will consider it as a risky investment and will assign very small part of company treasury for this investment.