‘It would be too welcome news to be true’ means that the good news has already come. Am I right?
No, it doesn’t. This is a hypothetical statement of the Conditional II type, which refers to the present:
“[If I heard that news,] it would be too welcome to be true.”
If the good news has already come, you say “It is too welcome to be true.”
Then, “[If I heard that news,] it would be too welcome to be true” has the meaning of ONLY IF i heard that news (where the news is not genuine real or existed just yet), it would be too welcome to be true, am I right in this context this time?
That’s right (or it exists, but you just haven’t heard it yet).
Oh I see it now, thanks a lot!