This is an issue I found in many companies, and it's been verified by friends and colleagues as a general problem.
Context: company, often a startup, which is cash-hungry or led by former salespeople (no technical leaders)
Problem: some manager or salesperson will generate hype by promising something that does not exist or which is outside the current roadmap. Senior management, by hearing the good news, will get immediately excited about the money coming in. The doers/engineers/technical people are then asked "when is this going to be ready". A normal, rational, technical person will consider the request and mention whether it is a) unfeasible, b) unprofitable, c) hard to do given the existing roadmap which has been carefully considered and shaped by multiple people in the company, or d) all these things together.
As somebody pointed out to me, "three months from now the senior manager won't even remember what this was about, but he will remember the enthusiasm and promise of the person who found this new opportunity, and the negativity and lack of collaborative spirit of the engineer who said it couldn't be done".
I see this happening regularly: somebody generates hype, engineers are left to deal with the consequences, and if one tries to discuss the topic he is told "well, do you want to be one who goes and explains the CEO this couldn't be done because you could not fit it in the roadmap?"
I have seen people surviving for years by contributing with little else than such hype. What is the most effective strategy to handle such a common occurrence?
Note: I wanted to add the tag "organisational behaviour" but couldn't find it.