A wave of deal activity has crashed into the health insurance world -- and Cigna investors are riding it higher.

Cigna (CI) shares spiked earlier in June after Anthem (ANTX) made a $47 billion bid to acquire the company. So far Cigna is playing hard to get, but investors seem to be betting a deal with someone will get done eventually.

Besides the Cigna/Anthem talks, the health insurance world is buzzing about a possible marriage of Aetna (AET) and Humana (HUM). There are also rumors that UnitedHealth (UNH) could get into the mix as well.

Related: Key to stock market growth in 2015: Lots of M&A

All of this shows how the Affordable Care Act, aka Obamacare, is changing the competitive landscape. The law, which the Supreme Court upheld a key provision of last week, has increased business through more customers. But it's also put pricing pressure on health insurers, prompting them to consider teaming up.