Halving reward, price effects? What is the case after halving reward takes place:

Would bitcoin price gets double, since its harder to mine? 

Would Blockchain introduces more blocks (e.g: 1/5mins)?
Will Bitcoin switch to a faster block rhythm?

No, the Blockchain will not change the number of blocks produced. That would require the difficulty retargeting rules to be changed, but the difficulty setting is part of the Consensus Rules, i.e. changing them would require a successful Hard Fork. There are currently no such plans.

Price

There is lots of speculation about price effects, but before we get to that, let's review the facts first.

Facts


Daily production is about 3600 bitcoins (~144*25)
The Halving will reduce this to about 1800 bitcoins per day
The timing of the halving can be predicted fairly accurately: 16th of July (± a few days)
We have data from the first Halving (2012-11-28), and numerous altcoin halvings
Price has been "fairly stable" between $152 and $502 (source Bitstamp) in the past year
Previous research showed that most bitcoins were not circulating, I assume this still is the case


Thoughts  


From [1.] daily production, [5.] price stability, and [6.] dormant bitcoins we can conclude that the market is soaking up more bitcoins worth more than 1,000,000 USD per day.
Reduced supply from [2.] would suggest an upward shift of market equilibrium.
Yet, the predictability of the supply event [3.] would suggest that such movements spread out due to anticipation, which aligns with the day of the [4.] first Halving only showing small price movements (+1.7%).
Reduced supply will also cause a steep decline in Mining profitability, may cause inefficient hardware to be sunsetted, or pointed at more profitable coins. E.g. the May'14 Dogecoin Halving [4.] caused difficulty to drop by ca. 25%. This effect should be less pronounced in Bitcoin, as more than half of the Bitcoin network's hash power came online over the last 6 months since the hash rate more than doubled.


Conclusions  


It is unreasonable to expect a sharp price increase around the Halving as the event is anticipated. The Halving effects would manifest ±6 months (guess!) around the Halving.
The price remains unpredictable: The longterm effects may have been mis-estimated by the market, leading to a subsequent correction (as with Litecoin's Halving in Aug'15), or a subsequent rally, as reduced supply takes effect.
Remember: There is a large number of other unknown events that will also affect the market.


So my final answer is: We don't know yet whether the price will double. It seems plausible for the exchange rate to rise above current levels.