So far Bombardier is working on the CS100 and CS300. Any doubts these aircraft will fly and dominate their market niche are naive.
What remains to be seen is when the company will announce stretching the CSeries platform beyond the 145-to-160 range. It's inevitable. Bombardier not only has a propensity towards doing stretches, but it also has great incentive to get into the larger narrow body commercial jet market - the sweet spot of this particular market.
This is one reason we have so much talk about CSeries competing against the 737 when in reality the current CSeries models target a market just below that with only slight overlap.
A recent article indicates the total backlog of 320s and 737s is now approaching a whopping 10,000. This makes it a very sweet space indeed. And its no wonder Airbus and Boeing are busting their butts in an effort to protect it.
Bombardier may have specific reasons for playing its cards close to the chest. If you intend to go head-to-head with couple of bulls, it probably doesn't make a lot of sense to announce it to them in advance.
On the other hand, Bombardier has paid fees to reserve the names "CS500" and "CS900", Why do this if you're convinced you'll never have the need to use them? By simply announcing the idea that Bombardier intends to build say, a 200, or a 250-seat commercial jet would attract a much higher number of orders, and would be easily financed because it requires only the addition of a "plug" to the fuselage.
Of course, wider wings and larger engines are usually added on larger models - still much cheaper than new designs. And not as much financing is required.
A Few thoughts on pricing
At that point, it might be a little more reasonable to compare the backlog of orders between these models, because each manufacturer would have an offering covering a similar market segment. At the same time, older aircraft generally cost less to produce.
Manufacturers tend to compete on the quality advantages of the product when it's new, and then give more emphasis to price as the production costs decline later in the cycle. Pricing is always a bit of a gamble. Sometimes you can make a splash by cutting your margins to the bone, but that approach can easily backfire if production costs rise unexpectedly.