Hi marrish, my friend I think that's a very reasonable suggestion - I have a couple of comments, though, about mamabhaviṣya-. Firstly, if we are to compound asmad- with bhaviṣya- we can't use the genitive singular. In compound, we would normally have mad-, i.e.: madbhaviṣya-. A good example of this we can find in the texts would be something like: matsakhi- "my friend". However, there is a rule (which is often violated) that a single word should not have two grammatical functions. So here, we have I/me as the subject of the verb (even though, here, you haven't actually included the subject aham overtly) and as the possessor of future in the genitive. I think, in general, the more usual construction would be to use sva-, so I would recommend the following ammendment:
^I was actually counting on you to chime in and I had a hard time weighing arguments pro and contra the use of sva as it would perhaps lend towards implying ''my own''. Your suggestion of using mad- is just perfect! Thank you.
Only other thing I'd suggest is that, by A. 8.4.59 वा पदान्तस्य, the substitution of anusvāra with a homo-organic nasal at the end of a word is optional. Visually I think it looks better as:
स्वभविष्ये वर्षां पश्यामि ।
It's also worth pointing out that in a hot and dry country like northern India, "seeing rains in the future" has a very different connotation than in English. Lots of poetry compares God or a lover to the longed-for rain cloud that will bring sweet relief and cooling rain at the end of the unbearable hot season. Although once the rains finally arrive, there's often too much, as this monsoon has once again sadly demonstrated. But in Sanskrit literature, when someone speaks about future rain, it's almost always with a positive connotation.