Try to keep up with emerging trends to see what you can be an early adopter of, such as how you list SSD hosting and CDN services. SSD is quickly becoming the standard, but a few years ago, being an early adopter should have definitely lead to increased sales if you were marketing that correctly.
Often times, you will see the needs of early customers lead to specializing in a certain niche, then word of mouth from them can help you grow. So it's important to pay attention to what your customers are asking for.
As to current areas where web hosts can try to look for growth, here are some, in no particular order. I think specialized CMS and ecommerce hosting still has some good growth areas, such as Wordpress + Woocommerce, Joomla, Magento, etc, niche focused hosting that is optimized for those CMS platforms. Turnkey e-com systems like Shopify and BigCommerce type sites, will continue to be popular, but, harder for the average hoster to jump into. The cloud sector will continue to mature and grow, it will be interesting to see which management systems take hold in that sector, and it's expensive to jump into correctly. The opportunity here is for those larger hosts that will specialize in providing private turnkey cloud systems. I think there is still good growth in remote backup services. Those that can truly provide good managed service should see solid growth if they can figure out the marketing side as well, and stay lean while they grow, as having top level techs 24/7 is not cheap. And while this one may sound self serving, there are solid numbers behind it, the CDN sector is estimated to grow by 30% annually through 2021, going from being just under a $5 billion per year sector in 2015 to an estimated $23 billion sector by 2021. You will start to see more hosts offering all inclusive business/ecommerce plans with CDN traffic, global DNS, remote backup service, etc, built into the plans as competition grows to get and maintain clients. I also think this period over the next 5 years will continue to see the trend of upper mid-sized and larger web hosts looking to grow through acquisition as opposed to spending money on advertising and marketing campaigns, as returns on the money trying to grow that way is tightening up and they see acquisition being a more cost effective way to grow. If you are a small to lower mid-sized host right now, and you can stay focused on what is working well for you, grow in that area, tighten up your financials and optimize your operating costs you could be in good shape to sell over the next few years.