My strategy is based on speculation, cloud mining and 5 years investment projection:

1. Buy when you think the price of bitcoin is going to rise

You bought 2 BTC, with 1 BTC = $700

2. When the price is high you can ether sell it or buy hashing power

For 1BTC=$1050 you can buy with 2BTC the 15 THS in genesis
For me 1 THS in genesis gives me around 0.00034 BTC per day so 15 THS gives 0.0051 BTC per day

3. The difficulty is unpredictable and it happens each 13 days approximately 

In 13 days 15 THS generates you 0.0663 BTC
If 1 BTC=$1050 so 0.0663 BTC=$69.615 you can buy 0.4641THS that generates 0.0001578 BTC per day
Your hashing power rose from 0.0051 to 0.0052578 or 3%
It means that if the difficulty is 5% you lost 2% of your mining power in the end of the day
Investing 2 BTC gives you 0.153 BTC each 30 days
If you count 5% difficulty each 15 days your ROI goes to 46.2 months=3years+10months+6days  (IF YOU SELL BTC AT $700 AND YOU DON'T REINVEST IT)
https://bitcoinwisdom.com/bitcoin/difficulty
( IF you reinvest everyday with BTC in the same price you can beat this symbolic 5% mining difficulty rise )

4. Accumulate your BTCs generated and multiply it speculating, selling, buying and reinvesting in hashpower

Now tell me, how much is gonna cost 1BTC in 5 years?

All my investments are in cloud mining and what worries me the most is the changes Segwit, Lightning and Teechan can cause in the mining difficulty. I have the impression that if those measures are taken combined over the next years they can break a good amount of bitcoin mining investors and this is imperatively going to influence my mining strategy. What are the best predictions and speculations about these changes? And most important, how many changes like this have taken place after bitcoin creation?

One possibility is Segwit is even more accepted and lightning or teechan is implemented. How can it retract the mining industry? I'm aiming for 1 year to have my investment back, but if I keep reinvesting it I will have all my investment in the miners and one of these changes can abruptly make it no more profitable.

Teechan:
https://cointelegraph.com/news/bitcoin-block-size-and-scaling-issues-may-be-solved-with-this-new-solution

PS: Those changes i'm talking about is those soft and hard forks that affects the amount of transactions that fits on a block, size of the block and so on

PS2: I know halving is going to be brought up in this discussion but we already know its effects and how mining difficulty is changed after this event, so i'm NOT really interested in this subject