Now, I know most people here want Suyash NOT to be the killer, but I am just noticing the evidence that would point to his being the killer, IF that is where Ekta wants to go. We know that Ekta can always change her mind at the last minute and make random people the killer, when she wants to get them temporarily out of the show - i.e. Nandini in the Gujral murder case, but IF Suyash IS the killer, here is some of the evidence for it:
In 18th July's eppy, SD blurts out something about Suyash having many rivals beause he likes to obliterate the competition. It sounded as if Suyash did that sort of thing regularly, and that would explain the Om-Rajeshwari Enterprises thing as well....also, SD talked about Suyash's anger and said that it was very hard to control Suyash when he got angry. Maybe in Om's case, Suyash did get angry beyond control and had him killed, later regretting his hasty decision? That would also explain his helping Parvati so much, because of his guilt.
Even SD, after mentioning Om, seemed scared of Suyash and his temper - so SOMETHING big must have happened in Om's case which caused SD to react like this - because after all, SD (as we very well know) is a certified villain, so what can have him scared, but a villain/mastermind bigger than his?
And we have to remember, that when Suyash was introduced, maybe he wasn't a villain per se, but he was a perfect businessman and one that would do ANYTHING to protect his business. It was only after meeting Parvati that he began to understand the importance of family. So it is very easy to assume that killing Om was a part of his business plan and was - he though - a necessary step to get rid of the competition and also to protect his company...
Another theory that I have is that Rajeshwari may be the name of - or related in another way to - Suyash's ex-wife. Maybe, Suyash and his ex-wife founded Rajeshwari Enterprises together (remember that disembodied hand signing Suyash's signature whilst the man himself sat elsewhere?) and Suyash had just warned Om (as in the letter) but the actual killing had taken place by the orders of his wife....even then, however, Suyash is not entirely blameless.
I am just floating the theory of Suyash's being the killer and trying to make some pieces fit. Who knows what Ekta Mai has in store for us, anyhoo...