Unfortunately the russians in their previous dealings with iran have proven themselves to be and this is putting it rather mildly quite,quite unreliable and untrustworthy in the extreme,one only has to look at the s300 debacle or the bushehr reactor to see this.Russia sadly has used iran as just a bargaining chip with the west in the past,now it is possible that with russian-western relations in the deep freeze and russia needing all the friends it can get then it might be more willing to play ball with iran,sadly tho rouhani and co seem more interested in trying to cozy up to the west than to try and take advantage of this,I mean ffs zarif didnt even bother to get the un arms embargo lifted as part of the jcpoa so russia cant even sell things like su30s and t90s to iran for another 3 years at least and a lot can happen in that space of time.Personally I ll believe the stories about t90s/su30s when I see the russians actually deliver them to iran,until then its just more bullsh!t.
I guess the hope that one can have is that Russian, under a newly enlightened Putin lead government. Will see Iran as an reliable partner (one that isn't afraid to have 100's possibly thousands die for their ally, Look at the Iranian death count in Iraq and Syria, it shows commitment). But as i've stated before there is a churning feeling in my gut that wants to say that Russia will get a better deal from a Trump led administration since Trump (Has STRONG Israeli JEWISH ties and his family is jewish, and his grandchildren are as well) meaning that Israel can easily sway Trump into doing what they want even if it means going it alone.
Putin must, AND I MEAN MUST, see this for the bigger picture. US has an overall goal with ever changing internal politics etc, etc... and that is Dominance, pure and simple.
Weapons transfer had deals like this probably won't go through. In fact I honestly think this deal will get torpedoed by
the US in someway shape or form. US will keep Iran at a certain military level where they think that striking Iran will be effective and won't lead to all out war (I don't agree with this mindset since Iran already progresses in many military fields regardless of Russian support, drones, cyber warfare, missiles of all types and land based weapon platforms).
I think one of the main reasons why Iran does need modern or modern-ish weapon systems is not so much the "need" but to get everyone else to shut up or at least bring their rhetoric down on how Iran is some ill-equiped rag tag militia trotting around as a full fledged professional force.
I still think Iran should just continue with their indigenous weapons program full speed. No outside support the better. Also 10 billion would be able to produce a lot of more missiles for Iran to add to its already MASSIVE missile stockpile. No matter how good a defense a country has there is no such thing as 100% missile defense.