Does creating a new business model mean that the current business model is challenged or should be changed?

Not always it could be a kind of innovation or new idea of a new bussiness model

Innovation or new ideas could be the reason for change in an organisation as rightly stated by Fredy. New Business model is also created if the "Organisational Objectives" are not being met and a change is required due obvious reasons. 

Intense competition can pose a chlallenge to the current business model and this may also be the reason for change as already stated in the question.

Its is all about sustaining your market position and fullfilling the future needs of business in terms of

competitive edge and  cost effectiveness .

According to the feasibility analysis, the problem may be related to the product, the customer need, or new strategy, or other reason.

change means previous one is not working for corpaorate .

Most of the time  ... YES ... this could be the case !!

One thing I do tell my clients in relation to "change management" that no one should feel bitter about change because change is the norm and it is really non-stoppable .     Furthermore,  introducing a change today in light of current changes and edevelopments does NOT mean that the decisions taken in the past were necessarily wrong !

They can simply be the right decisions at those times under those circumstances and conditions and specifics at that time .   

But there is also NO reason to stick to what was valid at those times, knowing that things have changed since then .

So , yes ... it would be expected that "new business modeling"  in new specifics /circumstances/developments would naturally challenge the existing business model and can possibly replace it !!!

1. Defined target markets are evolving faster than they used to, hence it's wise to tweak business models based on that if they help preserve/increase market share.
2. Sometimes rebranding/remodeling is required to bring an archaic brand to mazimise its brand equity.
3. Innovation/research and analysis are ongoing processes, and are a healthy sign in a growing or old business. There is no constant in life but change.

its depend on if the new if differant or in the same field

Nothing like challange but changing needs may be there.

Creating a new model for a new business does not mean the current model is threatened or should be changed. A new model often reinforces and complements the core business, as Dow Corning discovered.