The price of a bitcoin on the Genesis block website http://thegenesisblock.com/mining/a/254b3cc362 has been at $566 for about 2 weeks now. At first, I thought that the website had it pegged too low but then Coinbase and other exchanges seem to be moving toward that price. I've already bought about $4000 worth of btc on Coinbase recently when the price was about $650. I plan on spending about another G this friday; the price on Coinbase is about $580 right now. I personally would not wait for btc prices to drop below $400 because it may not happen. A news article tomorrow or the day after (for example) could send the prices skyrocketing again. I think bitcoins will reach $10,000 towards the end of this year.
My thoughts on mining now... At this point in the game, the idea of a company selling a mining machine is like selling a machine that literally makes money; it's an oxymoron. Some companies who just "loves" to make machine may do it just to do it but it would be rare for someone to give away a machine that makes profit. Bitcoins are no longer a speculation, it is money. I will still keep my eye out for any more new products from Bitmain since they do not sell pre-orders.