The cloud-based security services market is expected to top $2.1 billion by the end of this year, according to Gartner, and it will likely reach $3.1 billion in 2015. However, it's not all good news: Although cloud-based security revenue will remain strong, Gartner expects revenue opportunities to vary.

When it comes to the most sought-after cloud security services, things may seem a little predictable and unchanging. Gartner noted the top three will continue to be email security, web security services and identity and access management (IAM).

"The cloud-based security market remains a viable one, offering providers many opportunities for expansion," said Ruggero Contu, Research director at Gartner, in a prepared statement. "Encryption will be a new area of growth, but it remains a complex activity. The strongest interest will be in ecryption products from cloud security brokers, which are relatively easy to deploy and have options for on-premises encryption management."

It sounds like a good opportunity for the channel, particularly those who are positioning themselves as cloud services brokers and are adding cloud-based security services to their vetted offerings.

Through to the end of 2014, the highest growth is forecast to be in cloud-based tokenization and encryption, security information and event management (SIEM), vulnerability assessment and web application firewalls. There's huge growth potential, particularly in SIEM and IAM, although Gartner's Kelly Kavanaugh, principal research analyst, noted in a prepared statement the SIEM growth will be stemming from a small customer base.

Although cloud has often—particularly in past years—caused wariness among potential customers when it comes to security, more businesses will be turning to security-as-a-service offerings going forward. And according to Gartner, the cloud security market will grow faster than the market for remotely monitored customer premises equipment managed security services. It will start from a smaller base, though.

Over the next 24 months, expect the cloud security market, as well as the number of offerings, to grow considerably. It's the pure-play managed security services providers that will be most affected by this growth, and Gartner expects some consolidation within the space.